Such a latch is known from German 198 30 407 of Bender that serves to lock and unlock a roll bar that is part of an electromechanical roll-protection system. The latch has a two-armed lever that can move between a retaining position that locks a holder and one that releases the holder. One arm of the two-armed lever reaches around the holder in a retaining position and prevents movement of the roll bar into a crash-protection position. A spring urges the lever into a freeing position. A second lever is also constructed with two arms, one of which cooperates with the first lever and prevents it from pivoting into the freeing position. The second lever can be pivoted by an actuator, during which it loses contact with the first lever so that the latter can pivot freely into the freeing position. This state of the art has the disadvantage of a relatively large space requirement.
German 101 09 160 (US equivalent U.S. Pat. No. 6,623,073) of Schaefer describes another such system used on a so-called active motor-vehicle headrest, that is a headrest intended to move in a collision from a back rest position spaced well behind the head of the occupant of the seat on which the headrest is mounted to an advanced crash-protection position close behind the seat occupant's head. This system has a very complicated spring-loaded double-link assembly that is expensive to manufacture and prone to failure.